As with oil, the basic bulk trade in water will be by supertanker, supplemented perhaps by a tow of huge water bags shunting up and down the Pacific Coast from Alaska and Canada to parched Mexico and Southern California. Eventually, the business will shift to more economical pipelines. Water pipes will be laid along the same corridors that now carry oil and gas, adding political clout to the oil industry's plan to construct a gas pipeline from Alaska across Canada down into the U.S. Another scheme envisions damming James Bay, creating a great basin for clear drinking water. Canada's rivers run north, which means that water coming out of the north end of the James Bay basin would have to be reversed and run down a canal toward the East Coast of the U.S. American companies have long dominated the Canadian oil and gas business, but Canadians have fought hard to keep the U.S. from taking their water. Now with free-trade agreements between the U.S. and Canada, this may not be so easy, especially because Bush has said he views Canada's vast amounts of fresh water as a hemisphere-wide resource. Canada currently can supply up to 9 percent of the world's immediate need for fresh water and is thought to hold enough to potentially supply 25 percent of the overall need.

Other pipelines would be built from Austria, which draws water from the Alps, to Paris and elsewhere, and from Scotland down to London. Brazil, with its immense river systems, has a surplus of water. And China has substantial amounts of fresh water, although it's located in odd, hard-to-reach places.